[crystal-lang] Resolve type check compile error in ApiError

[usiegj00]

Displaying a rescue'd ApiError causes a compile-time error using crystal-lang v1.12.1. The @message instance variable is defined as String | Nil; however, even with a .nil? check, the variable causes a compile-time error when a further .empty? call is made.

The offending line uses the|| (logical OR) operator to ensure @message is not Nil. Although this should logically ensure that further operations on @message were only applied to @message when it is of type String, this is not what is seen during a compilation. It is unintuitive that this is necessary as crystal-lang's logical OR operator uses left-hand associativity.

This PR uses .try to make the .empty? call. Since Nil defines .try and ignores it, this achieves the same functional goal.

In lib/openapi_client/src/openapi_client/api_error.cr:32:31

 32 | if @message.nil? || @message.empty?
                                   ^-----
Error: undefined method 'empty?' for Nil (compile-time type is (String | Nil))

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